Childs Nerv Syst (2011) 27:1369–1373 DOI 10.1007/s00381-011-1472-3

CASE-BASED UPDATE

Absence of MRI abnormalities in severe spinal cord in children: case-based update

Martin M. Mortazavi & Nitin R. Mariwalla & Eric M. Horn & R. Shane Tubbs & Nicholas Theodore

Received: 18 November 2010 /Accepted: 19 April 2011 /Published online: 3 May 2011 # Springer-Verlag 2011

Abstract and spine injury. Based on the literature and our case Introduction Occult should be suspected illustration, we believe that the biomechanics of the based not only on the mechanism of trauma but also on the pediatric spine must be considered when children who age of the patient. The pediatric spine has unique may have sustained a SCIWORA are examined. biomechanical and anatomical properties that must be considered carefully when evaluating spinal cord trauma. Keywords Spinal cord injury . Pediatric spine . For instance, the hypermobility and elasticity of the spinal Tomography. MRI . Radiography. SCIWORA . Children . column in children often lead to self-reducing that Trauma . Biomechanics can mask spinal cord injury. Case illustration We present the case of a 22-month-old As defined by White and Punjabi, cervical spine instability male patient who was found to have ligamentous injury is loss of the ability of the spine to maintain its orientation detected by magnetic resonance imaging (MRI) in the so that there is no neurological injury, no deformity, and no upper cervical spine but missed by MRI in the lower incapacitating pain during normal activity [25]. As thoracic spine. Furthermore, there was no spinal cord injury evidenced by the literature and clinical experience, it is in the upper cervical spine, but indeed a serious insult in the not always obvious when the posttraumatic cervical spine is thoracic region. Since the advent of MRI, spinal cord injury unstable. Other regions of the spine can also be unstable without radiographic abnormality (SCIWORA) has become without radiographic evidence. increasingly rare but not altogether extinct. Clearing the cervical spine is challenging, especially in Conclusions We present a noteworthy example of the the pediatric population. Current guidelines require three- inadequacy of MRI in revealing SCIWORA, a term that is view radiography and thin-cut computed tomography (CT) antiquated as we combine the latest imaging techniques [10]. Yet occult spine injuries, which account for 40 to 70% with a better understanding of the biomechanics of trauma of pediatric cervical spine trauma, remain a major concern in pediatric trauma cases [12, 15]. Spinal cord injury without radiographic abnormality or SCIWORA is a term that was coined before the advent of magnetic resonance M. M. Mortazavi : N. R. Mariwalla : E. M. Horn : N. Theodore Division of Neurological Surgery, Barrow Neurological Institute, imaging (MRI). It refers to injuries that are most commonly St. Joseph’s Hospital and Medical Center, found in children. Phoenix, AZ, USA Although the pathophysiology of SCIWORA may be unique in the pediatric population, abnormalities on MRI R. S. Tubbs Pediatric Neurosurgery, are common features seen in adults and children. Moreover, Birmingham, AL, USA MRI is now a routine method for the evaluation of traumatic spine trauma (Table 1)[22]. Most patients with * R. S. Tubbs ( ) a spinal cord injury will exhibit some type of radiographic ACC 400 1600 7th Avenue South, Birmingham, AL 35233, USA abnormality. Because MRI is sensitive in identifying e-mail: [email protected] injuries to the spinal cord or surrounding soft tissues, 1370 Childs Nerv Syst (2011) 27:1369–1373

Table 1 Magnetic resonance a imaging protocol and detection Pathology Imaging technique of spinal cord abnormalities Acute cord hemorrhage Sagittal T2-weighted gradient-recalled echo [6] Acute posttraumatic disc herniation STIR Cervical spine alignment Sagittal T1-weighted spin-echo [14, 22] Vertebral body integrity Spinal cord swelling Spinal cord edema Sagittal T2-weighted spin-echo [14, 22, 26] STIR short tau-inversion recovery Compression a Axial T1- and T2-weighted Ligamentous hemorrhage spin-echo sequences can be used Paraspinal ligamentous injury STIR [14, 22, 26] to confirm all sagittal imaging Bone marrow edema findings contusions and hemorrhages, herniations, hematomas, and extremities. His pupils were pin point bilaterally. No blood ligamentous injury, it is a useful adjunct for the diagnosis of or cerebrospinal fluid was present in the ears, nose, or traumatic spinal cord injury. throat. His paraplegia failed to improve. Detecting a pediatric spine injury presents numerous CT of the head was negative for trauma, and the challenges that range from difficulty in performing neuro- predental interval was normal. CT of the thoracic and logical examinations to poor detection of ligamentous lumbar spine was negative; there was no evidence of injury on static radiographs to insufficient imaging studies. epidural hematoma in any region of the spine. MRI showed Occult injuries in SCIWORA are often discovered on MR the following neurological findings: a small amount of images. However, we present a case in which ligamentous subarachnoid hemorrhage (SAH) over the convexities and injury was detected in the upper cervical region but not in within the interpeduncular cistern, opacification of the the lower thoracic region of the same pediatric patient. mastoid air cells and paranasal sinuses, ligamentous injury at the atlanto-occipital and atlantoaxial junctions, a spinal cord hematoma and edema at T10–T11 without evidence of Case illustration ligamentous or bony injury of the thoracic or lumbar spine, and SAH within the lumber spinal canal. History Contrast-enhanced MRI of the entire spine showed normal alignment of the anterior and posterior spinal A 22-month-old Hispanic boy was ejected as an unre- elements and no evidence of subluxation. The vertebrae strained passenger in a motor vehicle accident. He was and disc spaces were normal, and no compression-type extricated by bystanders and brought to our facility by the fractures were identified anywhere in the spine. At the paramedics as a level 1 trauma patient. Initially, he was craniocervical junction, a marked short tau-inversion unable to move his upper right extremity, but he soon recovery (STIR) hyperintensity was present within the regained movement and localizing ability. At presentation, bilateral spaces between the occipital condyles and he could move neither lower extremity; this deficit has the lateral masses of C1. At T10–T11, a left eccentric remained and palpable pulses exist in both lower extrem- hematoma was surrounded by edema (Fig. 1). There was no ities. Extensive MRI showed a significant thoracic cord significant STIR intensity within the thoracic vertebral contusion without an associated fracture or ligamentous bodies or the thoracic paraspinous soft tissues (Fig. 2). injury. Spleen and kidney lesions and an unstable pelvic Hyperintense STIR signals were also noted within the fracture were also present. atlantoaxial articulations bilaterally and within the interspi- nous interval at C1–C2 (Fig. 3). Some layering of SAH was Examination and imaging studies present within the dependent portions of the lumbar spinal canal. All films were reviewed by neuroradiologists. The patient was intubated and sedated, which precluded a The patient was placed on steroids to treat his neurolog- good neurological examination. His rectal tone was ical complications. No further treatment was provided. decreased, and he was not moving his lower extremities. At presentation, he reportedly localized purposefully with his upper left extremity but only withdrew on the right. Discussion Eventually, he regained purposeful movement with his upper right extremity although still less than on his left side. Various features of the pediatric spine must be considered He did not withdraw or react to pain in the lower when a patient is evaluated for instability and spinal cord Childs Nerv Syst (2011) 27:1369–1373 1371

Fig. 1 Sagittal T2-weighted MRI of the thoracic spine demonstrating traumatic hematomyelia at the T10–T11 level (white arrow) injury. Our patient illustrates important aspects of the young Fig. 3 Sagittal MRI showing significant ligamentous injury on the spine that lead to unique injuries. In the immature spine, the STIR sequence at the upper cervical region (arrow) vertebrae have special characteristics that heighten inter- segmental mobility [13]. The vertebral bodies are wedged anteriorly, a configuration that enhances flexion and The spinous and transverse processes are less developed in forward translation [3, 6, 21]. Compared to the adult spine, children. Therefore, the musculature cannot transmit the the shallow facets are oriented more horizontally, contrib- same forces allowed by the longer mechanical levers uting to hypermobility during flexion, extension, and represented by adult processes. The intervertebral discs rotation [4, 6, 24, 25]. The uncinate processes, present in are also different; they help allow some motion between the adult vertebrae, are missing in children younger than bodies and the development of secondary lordoses. In the 10 years old [5, 23]. adult, they can attain 25% of the height of the vertebral Compared to the adult spine, the stabilizing forces of the body. In neonates, however, they are almost equal in height paraspinous musculature are reduced in the pediatric spine. to the vertebral body. In a child, the disc is rubbery and firm, more like that of a degenerated disc in an adult. With its tenacious attachment to the end plates, the disc frequently remains intact after severe spinal . The weak point is the interface between the end plate and vertebral body. A shear injury involving this site can cause the disc to penetrate the marrow of the vertebral body. The hyper- vascular growth zone in the endplate is brittle and easily splits from the primary centrum [2, 11]. Finally, the large head of the infant overwhelms the underdeveloped nuchal musculature, a notable cause of hyperextension and hyper- flexion injuries [17]. The elasticity of the ligaments of the spine, which connect the vertebrae, varies. For instance, the elasticity of the interspinous ligament is inversely proportional to a child’s age. The interspinous ligament also appears to generate little intervertebral tension, further contributing to hypermobility of the young spine until about 8 years of age [19]. Altogether, the biomechanics of the immature spine inherently increase the mobility of the spine at the expense Fig. 2 STIR sequence demonstrating lack of soft tissue injury at the of its protective function. In children, the elastic interspi- level of the thoracic spinal cord injury nous ligament combined with the malleable spinal column 1372 Childs Nerv Syst (2011) 27:1369–1373 can cause a self-reducing injury associated with a severe discrepancy in the sensitivity of MR imaging in detecting SCIWORA. the cervical and thoracic injuries deserves further investi- Atlanto-occipital dislocations are often associated with a gation and should prompt more careful imaging protocols. high-energy mechanism of trauma and are usually fatal. Fusion was not considered based on this special case and Recent advances in emergency medicine, however, have regarding the age of the patient. increased the frequency with which this type of injury The alignment of the thoracic spinal cord is evidence reaches medical attention [19]. In children, the occipital of the self-reducing capacity of the pediatric spine. The condyles are poorly developed, preventing stable atlanto- spinal cord hematoma may have been caused by occipital articulation and stability. Consequently, the pro- dislocation and immediate reduction or by a distracting pensity for dislocation is high [12, 27]. injury, which classically is associated with motor vehicle C1–C2 dislocations related to trauma have various accidents. In either case, MRI would be expected to causes and may be associated with fractures. They are reveal occult spinal instability associated with SCI- classified as either anterior, posterior, or rotatory. Because WORA (i.e., ligamentous injury of the thoracic spine). traumatic displacements of the atlantoaxial joint are Because it relies on past radiological and professional associated with severe ligamentous injury and protocols, SCIWORA can be a misleading term. MRI has [7], they are rarely seen in clinical settings. In fact, the reduced the number of SCIWORA cases, but under- atlantoaxial region is the level most commonly injured in standing pediatric pathophysiology should reduce this children. number further. This case highlights the inadequacy of The types of injury seen in the pediatric population MRI in detecting ligamentous injury in a patient with reflect the maturation of the extraneural components of the severe spinal cord injury. Further studies are needed to spine with age. For instance, the instability of the upper identify clinical scenarios and biomechanical factors that cervical spine in children leads to more upper spinal cord can help diagnose spinal instability when no radiographic lesions, especially in children under 9 years of age [16]. abnormalities are present. Thoracic lesions without radiographic abnormality seem to lack a discernible age distribution. However, Pang et al. found a small predilection for SCIWORA at T1–T6 in children under the age of 8 years [17]. 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